1. Field of the Invention
The present invention relates to a preparation method of carbon nanotubes and a catalyst for producing carbon nanotubes.
2. Related Art
Carbon nanotube is a material in which a six-membered ring network composed of carbon atoms is formed in a tubular shape. Recently, carbon nanotube which shows unique electronic behavior, characteristics that carbon nanotube is light weight and about 20 times stronger than steel, and the like have drawn attention, and thus the application of carbon nanotubes to the electronics field, the structural material field or the like has been expected.
As the application of carbon nanotubes to the electronics field, the application to field emission display (FED), flat fluorescent tubes, cathode devices between the cold cathodes and the like has been suggested based on characteristics of emitting electrons, for example, if an electric field is applied to the carbon nanotubes. In the case of these uses, dense and uniform emission of electrons is required, and thus it is necessary to uniformly arrange carbon nanotubes on the surface of a substrate.
As one of the methods for arranging carbon nanotubes to be formed on the surface of a substrate, Patent Document 1 suggested a method that iron chloride, which is a catalyst for forming carbon nanotubes, is carried on the surface of a substrate on which carbon nanotubes are formed and subsequently, carbon nanotubes are grown on the surface of the substrate by a chemical vapor deposition (CVD) method, which supplies the gas of hydrocarbon while the substrate is being heated. By this method, heating allows iron chloride, which is a catalyst, to be vaporized by sublimation from the surface of the substrate, and carbon nanotubes produced in the vapor phase by the vaporized catalyst are formed on the surface of the substrate.
Patent Document 1: Japanese Patent Application Laid-Open No. 2009-196873